The growing use of radio telephones, in particular mobile phones, has brought with it the desire and need to connect mobile phones to mobile office equipment. Users want, for example, to connect their portable computer via a radio connection formed by a radio telephone to another computer to permit data transfer between the two computers. Two essential considerations must be taken into account in the connection between the radio telephone and the computer. First, the modem to be installed in the computer is normally adapted for two-wire connection to the telephone network (PSTN) and this PSTN interface must be adapted to the radio telephone. Second, the control of the set-up, maintenance and disconnection of the radio telephone's transmission connection and, correspondingly, the control of the answering of the incoming call must somehow be arranged such that the communications software in the computer can control the connection.
To address the above-described need, an adapter device for use between a computer and a radio telephone has been developed, which is called, for example, a "teleadapter". One such known arrangement is shown diagrammatically in FIG. 1. FIG. 1 shows a two-wire "PSTN" connection 17 between a modem 4 and a teleadapter 20 (TA). The task of the teleadapter 20 is to carry out a conversion between the two-wire modem interface and the audio interface 16 of the mobile phone 1 and a control channel 15. An advantage of a solution of this kind is that the software (SW) of the computer 3 need not be specially adapted to mobile phone use since ordinary commercially available communications software which controls the set-up of the connection via the modem can be used in the computer. The teleadapter 20 identifies the control characters coming from the line 17 and converts them to the necessary radio telephone control signals on channel 15. On the other hand, the calls received by the radio telephone 1 are indicated on the control channel 15, and by means of this channel's detection signal, the teleadapter 20 forms the corresponding control signals, which pass to the line 17 to activate the computer and receive the call.
A drawback of the above solution is that the signal processing of the control channel calls for control logic in the teleadapter TA, for example, a microprocessor. A solution of this kind increases the total price of the connection arrangement and its complexity substantially.
A variation the above-described teleadapter is disclosed in patent WO 90/03076 (Method and Apparatus for Controlling Transmission of Voice and Data Signals). Naturally, the "teleadapter" described an also be located, for example, inside the computer as a discrete module and it can even be integrated into the modem. This arrangement never the less does not eliminate the above-mentioned. drawbacks related to the engineering design.
In a first aspect of the invention there is provided a connector assembly for a radio telephone and a computer, comprising a radio telephone adapter including external audio and control signal interfaces, a computer including a serial port connectable to the control signal interface, and a modem connectable to the computer and the external audio interface, wherein radio communication is set up by the radio telephone under control of signals from the serial port and data communication is achieved via the modem under control of the computer.
The advantage of the invention is that the heretofore complex logic necessary in the radio telephone adaptor is substantially dispensed with. Typically, the connection arrangement is divided into two parts: on the one hand, the adaptation of the levels of the connection wires is handled by matching circuits in the radio telephone's adapter part (cradle/connection wire, for example, in a car) and, on the other hand, all the control logic is adapted for this purpose in the computer's extended communications software. Physically, the connection arrangement in accordance with the invention comprises a serial communication bus to handle the control signals, a two-wire PSTN connection wire as well as the circuits in the radio telephone's teleadapter, by means of which circuits the signal levels of these lines are adapted for the radio telephone's internal connections.
An embodiment in accordance with the invention does not call for a large amount of equipment. The necessary level-matching circuits of the teleadapter are constructionally very simple and thus low in cost. Any substantially complex logic can be implemented in the computer. For example, the communications software in the computer may comprise two parts, one of which controls the modem and the other, via the serial communication bus, the setting up of the radio telephone's radio connection and if necessary answering of the incoming call. By means of the application program, it will be possible to control two physical interfaces, the serial port and the modem's bus interface. The duplication of the programming increases the costs somewhat but additional unit costs do not result from the actual electronics. Furthermore, there is greater flexibility in software applications than in hardware applications.
In a connection arrangement in accordance with the invention the electronic and physical construction of the serial communication bus, for example, RS232, can be known, and the logical signalling on the bus is determined on the basis of the signalling used by the internal control bus of the radio telephone in question.
In a connection arrangement in accordance with the invention, the signals to be transmitted on the audio channel of the modem and the radio telephone are conventional known telephone network signals. The computer modem can be a conventional external box modem or an internal card modem, with automatic ringing or without. In an arrangement in accordance with the invention use is not made of any features which the modem may offer for set-up of a connection, such as automatic ringing. Instead, functions connected with the transmission of payload data alone are used. The modem can also be a modem that transmits telefax signals or a corresponding signal converter.
The invention can be employed advantageously with cellular mobile phones.